Liquid immersion optical tool, method for cleaning liquid immersion optical tool, liquid immersion exposure method and method for manufacturing semiconductor device

ABSTRACT

There is disclosed is a liquid immersion optical tool, which comprises a light source, an optical lens system, a stage which moves an object base on which an object is to be placed, a head comprising a liquid immersion medium fluid supply device and a liquid immersion medium fluid discharge device to provide a layer of liquid immersion medium fluid between the optical lens system and the object, a fence which limits a region of the layer of liquid immersion medium fluid, and a cleaning device which cleans a portion having been contacted with the liquid immersion medium fluid by means of a cleaning solution.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Continuation-in-Part application of U.S. patent applicationSer. No. 11/217,464, filed Sep. 2, 2005, the entire contents of whichare incorporated herein by reference.

This application is based upon and claims the benefit of priority fromprior Japanese Patent Application No. 2004-258676, filed Sep. 6, 2004,the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid immersion optical tool, amethod for cleaning the liquid immersion optical tool, a liquidimmersion exposure method and a method for manufacturing a semiconductordevice, wherein a liquid immersion medium fluid layer is providedbetween an optical lens system and an object, improving an opticalperformance.

2. Description of the Related Art

A liquid immersion microscope or a liquid immersion exposure tool andthe like is used as a liquid immersion optical tool for immersing liquidimmersion medium fluid between an object and an optical lens system,thereby improving a resolution and a depth of focus. In a liquidimmersion microscope, a liquid immersion medium liquid such as oil orwater is provided between an objective lens of the microscope and anobject, thereby improving a resolution and a depth of focus. In a liquidimmersion exposure tool for use in a semiconductor lithography process,a liquid immersion medium fluid is provided between a lens and a wafer,thereby making it possible to increase NA (Numerical Aperture) and toincrease a depth of focus. This exposure tool is expected to be a mainexposure tool in manufacturing a semiconductor device in a generationfollowing a 65 nm half pitch generation (WO 99/49504).

The lens of the liquid immersion optical tool is in contact with liquidimmersion medium fluid for a long time when the liquid immersion opticaltool is used. Thus, there is a problem that substances generated fromthe tool, the object surface, and a structure for guiding the liquidimmersion medium fluid react with each other to adhere to the lens sothat the lens surface is clouded. This clouding of the lens surface isproblematic because it degrades the resolution and the luminescence.

In addition, there is a problem that the substance or impurities adheredto the lens or members of the tool contaminate the object surface.

In addition, portions having been contacted with the liquid immersionmedium fluid include a liquid immersion head, an object stage, and aliquid immersion medium fluid supply and discharge device. There is aproblem that, when the liquid immersion optical tool is used for a longtime, impurities adhere to their associated portions, and the adheredimpurities reach an object and contaminate the object surface.

Furthermore, there is a problem that, when the liquid immersion mediumfluid supplied between the lens and the wafer is not clean before andduring exposure, the exposure cannot be properly carried out.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provideda liquid immersion optical tool comprising:

a light source;

an optical lens system;

a stage which moves an object base on which an object is to be placed;

a head comprising a liquid immersion medium fluid supply device and aliquid immersion medium fluid discharge device to provide a layer ofliquid immersion medium fluid between the optical lens system and theobject;

a fence which limits a region of the layer of liquid immersion mediumfluid; and

a cleaning device which cleans a portion having been contacted with theliquid immersion medium fluid by means of a cleaning solution.

According to a second aspect of the present invention, there is provideda cleaning method in the liquid immersion optical tool comprising alight source; an optical lens system; a stage which moves an object baseon which an object is to be placed; a head comprising a liquid immersionmedium fluid supply device and a liquid immersion medium fluid dischargedevice to provide a layer of liquid immersion medium fluid between theoptical lens system and the object; a fence which limits a region of thelayer of liquid immersion medium fluid; and a cleaning device whichcleans a portion having been contacted with the liquid immersion mediumfluid by means of a cleaning solution, wherein the portion having beencontacted with the liquid immersion medium fluid is cleaned for apredetermined time by means of the cleaning device.

According to a third aspect of the present invention, there is provideda semiconductor device manufacturing method in which a semiconductordevice is manufactured by using a liquid immersion exposure tool, theliquid immersion exposure tool comprising:

a light source;

an optical lens system;

a stage which moves an object base on which an object is to be placed;

a head comprising a liquid immersion medium fluid supply device and aliquid immersion medium fluid discharge device to provide a layer ofliquid immersion medium fluid between the optical lens system and theobject;

a fence which limits a region of the layer of liquid immersion mediumfluid; and

a cleaning device which cleans a portion having been contacted with theliquid immersion medium fluid by means of a cleaning solution.

According to a fourth aspect of the present invention, there is providea liquid immersion optical tool comprising:

a light source;

an optical lens system;

a stage which moves an object base on which an object is to be placed;

a liquid supply device which supplies a liquid immersion medium fluid ora cleaning solution between the optical lens system and the object;

a liquid discharge device which discharges the liquid immersion mediumfluid or the cleaning solution; and

an ozone gas supplying device which is connected to the stage or theliquid supply device and supplies an ozone gas to the cleaning solution.

According to a fifth aspect of the present invention, there is provide aliquid immersion optical tool comprising:

a light source;

an optical lens system;

a stage which moves an object base on which an object is to be placed;

a liquid supply device which supplies a liquid immersion medium fluid ora cleaning solution between the optical lens system and the object;

a liquid discharge device which discharges the liquid immersion mediumfluid or the cleaning solution; and

a measuring device which is connected to the liquid discharge device andmeasures at least one of a dissolved gas concentration and a particledensity of the liquid immersion medium fluid or the cleaning solutiondischarged by the liquid discharge device.

According to a sixth aspect of the present invention, there is provide acleaning method which cleans an optical lens system in a liquidimmersion optical tool comprising:

a light source;

the optical lens system;

a stage which moves an object base on which an object is to be placed;

a liquid supply device which supplies a liquid immersion medium fluid ora cleaning solution between the optical lens system and the object;

a liquid discharge device which discharges the liquid immersion mediumfluid or the cleaning solution; and

an ozone gas supplying device connected to the stage or the liquidsupply device, the method comprising:

cleaning the optical lens system by the cleaning solution in which anozone gas is dissolved by supplying the ozone gas from the ozone gassupplying device to the cleaning solution.

According to a seventh aspect of the present invention, there is providea liquid immersion exposure method in a liquid immersion optical toolcomprising:

a light source;

an optical lens system;

a stage which moves an object base on which an object is to be placed;

a liquid supply device which supplies a liquid immersion medium fluid ora cleaning solution between the optical lens system and the object;

a liquid discharge device which discharges the liquid immersion mediumfluid or a cleaning solution; and

a measuring device which is connected to the liquid discharge device andmeasures a dissolved gas concentration in the liquid immersion mediumfluid or the cleaning solution discharged by the liquid dischargedevice, the method comprising:

carrying out a liquid immersion exposure when the dissolved gasconcentration measured by the measuring device is a predeterminedconcentration or less.

According to an eighth aspect of the present invention, there is providea liquid immersion exposure method in a liquid immersion optical toolcomprising:

a light source;

an optical lens system;

a stage which moves an object base on which an object is to be placed;

a liquid supply device which supplies a liquid immersion medium fluid ora cleaning solution between the optical lens system and the object;

a liquid discharge device which discharges the liquid immersion mediumfluid or the cleaning solution; and

a measuring device which is connected to the liquid discharge device andmeasures a particle density in the liquid immersion medium fluid or thecleaning solution discharged by the liquid discharge device, the methodcomprising:

carrying out a liquid immersion exposure when the particle densitymeasured by the measuring device is a predetermined density or less.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a view showing a configuration of a liquid immersion exposuretool according to a first embodiment of the present invention;

FIG. 2 is a view showing an example of a cleaning device according tothe first embodiment of the present invention;

FIG. 3 is a view showing another example of the cleaning deviceaccording to the first embodiment of the present invention;

FIG. 4 is a view showing another example of the cleaning deviceaccording to the first embodiment of the present invention;

FIG. 5 is a view showing a configuration of a liquid immersion exposuretool according to a second embodiment of the present invention;

FIG. 6 is a view showing a configuration of a liquid immersion exposuretool according to a third embodiment of the present invention;

FIG. 7 is a view showing a configuration at the time of exposure of aliquid immersion exposure tool according to a fourth embodiment of thepresent invention;

FIG. 8 is a view showing a configuration at the time of cleaning of theliquid immersion exposure tool according to the fourth embodiment of thepresent invention;

FIG. 9 is a view showing another configuration at the time of cleaningof the liquid immersion exposure tool according to the fourth embodimentof the present invention;

FIG. 10 is a view showing a configuration at the time of exposure of aliquid immersion exposure tool according to a fifth embodiment of thepresent invention;

FIG. 11 is a flowchart of a liquid immersion exposure method accordingto the fifth embodiment of the present invention;

FIG. 12 is a view showing another configuration at the time of exposureof the liquid immersion exposure tool according to the fifth embodimentof the present invention;

FIG. 13 is a flowchart of a liquid immersion exposure method accordingto the fifth embodiment of the present invention;

FIG. 14 is a view showing a further configuration at the time ofexposure of the liquid immersion exposure tool according to the fifthembodiment of the present invention;

FIG. 15 is a flowchart of a liquid immersion exposure method accordingto the fifth embodiment of the present invention;

FIG. 16 is a view showing a configuration at the time of cleaning of aliquid immersion exposure tool according to a sixth embodiment of thepresent invention;

FIG. 17 is a flowchart of a liquid immersion exposure method accordingto the sixth embodiment of the present invention;

FIG. 18 is a view showing another configuration at the time of cleaningof the liquid immersion exposure tool according to the sixth embodimentof the present invention;

FIG. 19 is a flowchart of a liquid immersion exposure method accordingto the sixth embodiment of the present invention;

FIG. 20 is a view showing a further configuration at the time ofcleaning of the liquid immersion exposure tool according to the sixthembodiment of the present invention;

FIG. 21 is a flowchart of a liquid immersion exposure method accordingto the sixth embodiment of the present invention;

FIG. 22 is a view showing a configuration at the time of cleaning byozone water, of the liquid immersion exposure tool according to thesixth embodiment of the present invention; and

FIG. 23 is a view showing another configuration at the time of cleaningby ozone water, of the liquid immersion exposure tool according to thesixth embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of the present invention will be described withreference to the accompanying drawings.

First Embodiment

FIG. 1 is a view showing an outline configuration of a liquid immersionexposure tool according to a first embodiment of the present invention.A reticle stage 31 is provided under a lighting optical system (lightsource) 20. A reticle 32 which is a photo mask is placed on the reticlestage 31. The reticle stage 31 is movable in parallel to an object base37 (i.e., in a horizontal direction in the exposure tool). A projectionlens system (optical lens system) 33 is provided under the reticle stage31. The object base 37 is provided under the projection lens system 33.A semiconductor substrate 10 is placed on the object base 37. Theheights of the surface of the semiconductor substrate 10 and part of theobject base 37 near the semiconductor substrate 10 are almost equal toeach other. The object base 37 is movable together with a stage 34 andthe semiconductor substrate 10 in the parallel direction and theorthogonal direction to the reticle stage 31 (i.e., horizontal andvertical directions in the exposure tool). The stage 34 can be inclinedwith respect to the horizontal plane.

A fence 35 is mounted at the lower part of the projection lens system33. A liquid immersion medium fluid supply and discharge mechanism isprovided at the side of the projection lens system 33. The supply anddischarge mechanism comprises a pair of liquid immersion medium fluidsupply and discharge devices 36 which supply liquid immersion mediumfluid into the fence 35, and discharge the liquid immersion medium fluidfrom the fence 35. A structure of the liquid immersion medium fluidsupply and discharge mechanism is not limited to this structure. Whenone of the pair of liquid immersion medium fluid supply and dischargedevices 36 functions as a liquid immersion medium supply device, theother liquid immersion medium fluid supply and discharge devicefunctions as a liquid immersion medium discharge device. That is, thepair of liquid immersion medium fluid supply and discharge devices 36functions complementarily with respect to the supply and discharge ofthe liquid immersion medium fluid. During exposure, a space between thesubstrate 10 and the projection lens system 33 surrounded by the fence35 is filled with a layer of liquid immersion medium fluid, for example,water, supplied from one of the liquid immersion medium fluid supply anddischarge devices 36. Light of exposure emitted from a light source 20reaches the semiconductor substrate 10 placed on the object base 37 viaa mask pattern (i.e., a semiconductor element pattern) of the reticle32, the projection lens system 33 and the liquid immersion medium fluidlayer. In this manner, an image of the mask pattern of the reticle 32 isprojected on a photo resist film provided on the semiconductor substrate10 so that a latent image is formed on the photo resist film. Astructure formed of the fence 35 and the pair of the light immersionmedium fluid supply and discharge devices 36 is called a head.

A pair of cleaning devices 38 are connected to a pair of the liquidimmersion medium fluid supply and discharge devices 36 in order to defogthe projection lens system 33 and remove impurities adhered at the timeof exposure. The pair of the cleaning devices 38 complementarily supplya cleaning solution into the fence 35 via the pair of the liquidimmersion medium fluid supply and discharge devices 36. After exposure,the cleaning solution is supplied into the fence 35, whereby parts orportions having been contacted with the liquid immersion medium fluidsupplied from the liquid immersion medium fluid supply device 36 arecleaned.

In a step and scan type exposure tool, all of the patterns on a photomask are not collectively transferred to a resist laminate film. Only apattern portion of the entire pattern of the photo mask, which issmaller than the entire pattern of the photo mask, is collectivelytransferred. The pattern portion is a slit shape predetermined areacalled an exposure field. Exposure is carried out in a state in whichthe photo mask and the substrate are moved at a rate according to amagnification of the projection optical system, whereby the photo maskand substrate are scanned by light ray to project the entire pattern ofthe photo mask onto the resist laminate film. The term “exposure field”may mean the predetermined area of the slit shape on the substrate planewhich is optically conjugate with the pattern side on the photo mask.

A photo mask movement distance is greater than a substrate movementdistance. Thus, in general, the number of photo mask movements isreduced in order to reduce an exposure process time. Therefore, it isgeneral that relative movement directions of the photo mask andsubstrate are opposite to each other between the unit exposure regionsin which the exposure sequence is continuous.

The relative movement directions (scan directions) of the photo mask andsubstrate are changed depending on the unit exposure regions. Therefore,the supply/discharge functions of the pair of the liquid immersionmedium fluid supply and discharge devices 36 are complementarily changedto be supply/discharge according to the scan direction so that anorientation of the liquid immersion medium fluid flow is changed. Inaddition, it is possible that one of the cleaning devices 38 is operatedaccording to the scan direction so that a cleaning solution may besupplied from the one cleaning device 38 into the fence 35 via thecorresponding liquid immersion medium fluid supply and discharge device36, and the liquid immersion medium fluid supply and discharge device 36connected to the other inactive cleaning device 38 is operated so thatthe cleaning solution after being used may be discharged from the fence35 by means of the other liquid immersion medium fluid supply anddischarge device 36.

A pattern region on the photo mask may be restricted by means of adiaphragm called a mask blind. A region of a resist film on which alatent image corresponding to the mask pattern on the photo mask is tobe formed (unit exposure region) may be called an exposure shot.

Now, cleaning after exposure will be described. Function water such asozone water, ionized water, carbonated water, or peroxide water is usedas a cleaning solution. Alternatively, acid is used as a cleaningsolution. However, when acid is used as a cleaning solution, the lenssurface is corroded so that the lens performance may change. Thus, it ispreferable that function water be used as a cleaning solution. Inaddition, cleaning may be carried out with water vapor.

The cleaning solution is supplied into the fence 35 in a state in whichcavities are provided. It is preferable that the cavities bemicro-cavities whose average in diameter is 1 μm or less. Themicro-cavities have long service life, and are unlikely to disappearbefore they reach the top of the substrate.

An ultrasound wave, a water jet, or a cavitation jet can be used inorder to generate cavities in a cleaning solution. For example, cavitiesare generated in the cleaning solution by means of a cavitation jetnozzle shown in FIG. 2 or a venturi tube shown in FIG. 3. In FIG. 2,reference numeral 41 denotes a high pressure water nozzle from which ahigh pressure cleaning solution flows; reference numeral 42 denotes alow pressure nozzle from which a low pressure cleaning solution flows;and reference numeral 43 denotes a mixing portion. In FIG. 3, referencenumeral 44 denotes a low speed flow section, and reference numeral 45denotes a high speed flow section.

The cavitation jet nozzle of FIG. 2 is disclosed in detail intransactions of Japanese Machinery Society (Edition B), Volume 67, Issue653 (2001-1), pp. 88, Transaction No. 00 to 0620. In general, cavitationjet cleaning is a cleaning method efficiently utilizing a physical forcefrom which there occurs a cavitation phenomenon usually desired to beavoided in fluid engineering. If a pressure lower than a saturated vaporpressure is generated in fluid, cavities occur. The cavities aredestroyed if the pressure in the fluid is returned to a pressure higherthan the saturated vapor pressure, and at this time, a high pressure ismomentarily generated.

The cavitation jet shown in FIG. 2 is designed so that a speeddifference in water flow occurs on a boundary between the high speedwater discharged from the high pressure nozzle 41 and the low speedwater discharged from the low pressure nozzle 42.

The venturi tube 38 of FIG. 3 can be used as a device for generatingcavities. When a fluid passes from a nozzle 44 having a large aperturevia a nozzle 45 having a small aperture, cavities occur in the fluid,since the speed of the fluid changes from a low speed at the nozzle 44to a high speed at the nozzle 45.

In addition, a Pitot tube of FIG. 4 can be used as a device forgenerating cavities. In FIG. 4, reference numeral 46 denotes a highpressure nozzle, and reference numeral 47 denotes a low pressure nozzle.

During cleaning, a cleaning solution containing cavities is suppliedfrom the cleaning device 38 into the fence 35, while the stage 34 onwhich the semiconductor substrate 10 is placed is moved and accordinglythe semiconductor substrate 10 is moved. Cleaning is carried out whilemoving the semiconductor substrate 10, thereby making it possible toclean parts or portions having been contacted with the liquid immersionmedium fluid used during exposure. The parts or portions having beencontacted with the liquid immersion medium fluid include the projectionlens system 33, the fence 35, the object base 37, the stage 34, and theliquid immersion medium fluid supply and discharge devices 36.

Now, a cleaning period will be described. For example, after exposurehas been carried out for a predetermined time, a cleaning process iscarried out. In one option, a measuring instrument for measuringintensity of light transmitting the projection lens system 33 (exposurelight wavelength is preferable) is provided at the liquid immersionexposure tool, and the light intensity is measured by means of themeasuring instrument after exposure has started so that a cleaningprocess may be carried out when the measured light intensity becomessmaller than a preset value. In another option, in addition to theabove-described measuring mechanism, there are further provided: acomputing mechanism for computing a lowered quantity of light intensityfrom information on the light intensity measured by the measuringmechanism; and a calculating mechanism for calculating a cleaning periodfrom the computed lowered quantity of light intensity, for carrying outthe cleaning process in a computed cleaning period.

In addition, after the cleaning process has been carried out, a rinseprocess may be carried out using a rinse solution in which no cavitiesexist. By supplying the rinse solution, the cleaning solution whichremains in the liquid immersion exposure tool can be removed. Water isused as a rinse solution. For example, by supplying water as a rinsesolution from the liquid immersion medium fluid supply and dischargedevice 36, the inside of the liquid immersion exposure tool is rinsed,thereby removing the cleaning solution which remains in the liquidimmersion exposure tool.

A cleaning process is carried out using the above-described cleaningdevice, thereby making it possible to remove the cloudiness of the lensand to recover the resolution and luminescence. In addition, thesubstance or impurities adhered to the lens or members of the toolduring exposure can be removed, and an object surface can be restrictedfrom being contaminated.

In addition, the liquid immersion exposure tool comprises a cleaningdevice, thereby making it possible to facilitate a cleaning process andto reduce a maintenance time. By reducing the maintenance time, anequipment operation time is enhanced, and a manufacturing cost of amanufactured semiconductor element can be reduced.

Second Embodiment

The present embodiment shows an example which is different from that ofthe liquid immersion exposure tool shown in FIG. 1. FIG. 5 is a viewshowing a liquid immersion exposure tool according to a secondembodiment of the present invention. The same elements are designated bythe same reference numerals. A duplicate description is omitted here.

In the liquid immersion exposure tool shown in FIG. 5, a cleaning device58 is provided to be opposed to a substrate face of the projection lenssystem 33. The cleaning device 58 is detachable from the liquidimmersion exposure tool.

Third Embodiment

The present embodiment shows another example which is different fromthat of the liquid immersion exposure tool shown in FIG. 1. FIG. 6 is aview showing a liquid immersion exposure tool according to a thirdembodiment of the present invention. The same elements are designated bythe same reference numerals. A duplicate description is omitted here.

In the liquid immersion exposure tool shown in FIG. 6, a cleaning device68 is provided at the back surface of the stage 34, and the cleaningdevice 68 moves together with the stage 34.

Fourth Embodiment

FIG. 7 and FIG. 8 are views showing a liquid immersion exposure toolaccording to a fourth embodiment of the present invention. FIG. 7 showsa configuration of the liquid immersion exposure tool at the time ofexposure, and FIG. 8 shows a configuration of the liquid immersionexposure tool at the time of cleaning. The same parts or components asthose in the first to third embodiments are designated by the samereference numerals, and the description thereof is omitted.

A liquid supply device 76 and a liquid discharge device 79 are providedand connected to a fence 35. The liquid supply device 76 supplies aliquid into the fence 35, and the liquid discharge device 79 dischargesthe liquid from the fence 35. The structures of the liquid supply device76 and the liquid discharge device 79 are not limited. The fence 35, theliquid supply device 76, and the liquid discharge device 79 are called ahead unit.

At the time of exposure, the space between the substrate 10 and theoptical lens system 33 is filled with a liquid immersion medium fluidsupplied from the liquid supply device 76. Exposure light emitted fromthe optical lens system 33 reaches an irradiation region through theliquid immersion medium fluid, so that a mask pattern (a semiconductordevice pattern) on the reticle 32 is projected on a photoresist film ona surface of the substrate, which is in the irradiated region, tothereby form a latent image on the photoresist film.

A cleaning device 38 is connected to the liquid supply device 76, andthe cleaning device 38 supplies, for example, ultrapure water, as acleaning solution into the fence 35 via the liquid supply device 76.Further, the cleaning device 38 generates cavities (air bubbles) in thecleaning solution. The liquid supply device 76 may be configured tosupply ultrapure water.

The cleaning device 38 generates cavities in the cleaning solution byusing an ultrasound wave, a water jet, or a cavitation jet, etc. It ispreferable that the cavities are micro-cavities whose average indiameter is to 1 μm or less, and which have long service life and areunlikely to disappear before the cavities reach the substrate. Thedevices shown in FIGS. 2 to 4 can be used as a device for generatingcavities.

In this embodiment, as shown in FIG. 8, an ozone gas supply portion 82is provided immediately beneath a portion of the stage 34 where the headunit contacts. At the time of cleaning, ozone gas is directly suppliedinto the fence 35 from the ozone gas supply device 84 via the ozone gassupply portion 82.

The ozone gas supplied from the ozone gas supply device 84 via the ozonegas supply portion 82 dissolves into the cleaning solution in the fence35, whereby ozone water is formed. Moreover, cavities are generated inthe ozone water by the cleaning device 38, and the optical lens system33 and the head unit are cleaned with the ozone water containingcavities. By using ozone water, the lens surface can be effectivelycleaned without being damaged. In addition, since the ozone watercontains cavities, the cleaning effect is improved.

Ozone water is stable in a liquid state under pressure, or at anextremely low temperature. However, ozone water is vaporized in a statenot under pressure, or in a state under increased temperature.Accordingly, in a case of a system in which ozone water is led into thefence from a long distance, the pipe extending to the lead-in portionmust be maintained in a state under pressure, and the temperature mustbe maintained at a low temperature. However, it is difficult to realizethese requirements.

To avoid the difficulty as described above, the present embodiment hasthe following configuration, as shown in FIG. 8. That is, the ozone gassupply portion 82 is provided immediately beneath portions to becleaned, so that an ozone gas is directly supplied to the regionsurrounded by the fence 35 and the ozone gas is dissolved into thecleaning solution, that generates ozone water. Cleaning is performed ina state in which the cleaning solution has become ozone water, whilegenerating cavities in the ozone water in the fence 35 by the cleaningdevice 38. In this way, the difficulty in realization by theabove-described lead-in system is solved.

As another configuration of the present embodiment, as shown in FIG. 9,the ozone gas supply portion 82 is connected to the liquid supply device76 to introduce ozone gas into the liquid supply device 76 through theozone gas supply portion 82 from the ozone gas supply device 84, wherebya cleaning solution, for example, ultrapure water, may be made to beozone water in the liquid supply device 76. In any case, ozone gas issupplied to the portion near to the objects to be cleaned such as theoptical lens system 33, the stage 34, and the fence 35, etc. which havebeen contacted with the medium fluid used at the time of liquidimmersion exposure. Consequently, cleaning by ozone water can beattained, and the optical lens system 33, the stage 34, and the fence 35can be effectively cleaned, with the lens surface being not damaged.

Since in this embodiment ozone gas is supplied to the region to becleaned from the portion near to the region to be cleaned, it ispossible to carry out cleaning process without damaging the lenssurface. This cleaning process makes it possible to remove fog over thelens, which can improve the resolution of the optical lens system 33. Atthe same time, substances and contaminations adhered to the lens ormembers of the tool at the time of liquid immersion exposure can beremoved, which makes it possible to reduce contamination on an objectsurface.

After the cleaning process has been performed, rinsing may be carriedout using a rinse solution, for example, water, in which no ozone andcavities exist. By supplying the rinse solution, the cleaning solutionremaining in the liquid immersion exposure tool can be removed. Forexample, the rinse process may be carried out by supplying water fromthe liquid supply device 36.

In a case of a configuration of FIG. 9, cleaning can be performed whilemoving the substrate 10 in the same way as in the time of liquidimmersion exposure of the device shown in FIG. 7, so that the objectbase 37 and the like can be cleaned.

Fifth Embodiment

FIG. 10 is a view showing a configuration at the time of exposure of aliquid immersion exposure tool according to a fifth embodiment of thepresent invention. In the same way as the configuration of the liquidimmersion exposure tool shown in FIGS. 7 and 8, there are provided alighting optical system (light source) 20, a reticle stage 31, a reticle32, an optical lens system (projection lens system) 33, a stage 34, afence 35, a liquid supply device 76, and a liquid discharge device 79.

In the present embodiment, a dissolved gas concentration meter 86 isfurther provided and connected to the liquid supply device 79. Thedissolved gas concentration meter 86 monitors during exposure aconcentration of the dissolved gas (for example, nitrogen, oxygen, orthe like) contained in the liquid immersion medium fluid discharged fromthe fence 35 by the liquid supply device 79.

At the time of exposure, the space between the substrate 10 and theoptical lens system 33, which is in a region surrounded by the fence 35,is filled with a layer of a liquid immersion medium fluid, for example,water. Exposure light emitted from the optical lens system 33 reaches anirradiation region through the liquid immersion medium fluid layer. Animage of the mask pattern (semiconductor device pattern) on the reticle32 is projected on a portion of a photo resist on the substrate surface,which portion corresponds to an irradiation region, so that a latentimage is formed in the photo resist film.

In some cases, the liquid immersion medium fluid may be forced out ofthe wafer during a process of carrying out the liquid immersionexposure, for example, when an edge of the wafer is exposed by theexposure head. In such a case, air existing in a gap between the wafercassette (object base) and the wafer is introduced in the liquidimmersion medium fluid, and dissolved in the liquid immersion mediumfluid. When the air dissolved in the liquid immersion medium fluidexcesses over a given amount, there is a possibility that bubbles aregenerated about in the liquid immersion medium fluid due to a rise intemperature occurred by light irradiation at the time of exposure, whichmakes the exposure defective.

It is possible to judge whether or not the liquid immersion medium fluidfor liquid immersion exposure is under the appropriate condition bymonitoring whether or not the concentration of the dissolved gas (forexample, nitrogen, oxygen, or the like) in the liquid immersion mediumfluid discharged from the fence 35 by the liquid supply device 79 is apredetermined concentration or less, for example, 0.1 ppm or less.

When it is judged during the exposure that the above-described conditionis not satisfied, it is determined that abnormality has been detected,and a re-work is carried out, that is, a re-coating of resist isperformed and a lithography process is again performed. After thelithography process has been performed, the concentration of thedissolved gas is monitored with the dissolved gas concentration meter 86again. When it is judged that the condition in which the concentrationof the dissolved gas is a predetermined concentration or less, forexample, 0.1 ppm or less, is satisfied so that no abnormality isdetected, the liquid immersion exposure is re-started.

FIG. 11 is a flowchart showing an example of the liquid immersionexposure method in the just-mentioned case. During the exposure (step501), the concentration of the gas dissolved in the liquid immersionmedium fluid discharged from the fence by the liquid supply device 79 ismonitored by the dissolved gas concentration meter 86 in appropriatetimings or continuously, and it is judged whether or not the conditionis satisfied in which the concentration of the dissolved gas is apredetermined concentration or less, for example, 0.1 ppm or less (step502). When the condition is not satisfied, the exposure is stopped, andre-work is carried out, that is, a re-coating of resist is performed anda lithography process is again performed (step 504). When the conditionis satisfied, the exposure is continued (step 503).

Further, as shown in FIG. 12, a particle counter 88 may be connected tothe liquid discharge device 79, in place of the dissolved gasconcentration meter 86. The particle counter 88 monitors particlesincluding gas (air bubbles) as a laser scatter or contaminants in aliquid, for example, in the liquid immersion medium fluid. The particlecounter 88 monitors whether or not a particle density is a predetermineddensity, for example, one piece/ml or less, and detects an abnormal whenthe particle density is greater than the predetermined density. It isdifficult for an existing particle counter to distinguishably countparticles and bubbles in the liquid. However, because both of particlesand bubbles affect the liquid immersion exposure, the above-describeddetection of abnormality by the particle counter 88 is effective.

When the liquid immersion exposure is carried out onto the edge of thewafer, for example, as described above, air existing in a gap betweenthe wafer cassette (object base) and the wafer may be introduced as airbubbles into the liquid immersion medium fluid, or contaminants adheredto the wafer edge may be introduced into the liquid immersion mediumfluid by friction at the time of handling the wafer.

When a large amount of gas (air bubbles) as a laser scatter and/orparticles including contaminants is contained in the liquid immersionmedium fluid, the exposure results in failure. Therefore, it isadvantage to monitor the amount of gas and/or particles and determinewhether or not the liquid immersion medium fluid is under an appropriatecondition for exposure.

FIG. 13 is a flowchart showing an example of the liquid immersionexposure method in the just-mentioned case. During the exposure (step701), the density of the particle contained in the liquid immersionmedium fluid discharged from the fence 35 by the liquid supply device 79is monitored by the particle counter 88 in appropriate timings orcontinuously, and it is determined whether or not the condition issatisfied in which the particle density is a predetermined density, forexample, one piece/ml or less (step 702). When the condition is notsatisfied, the exposure is stopped, and a re-work is carried out, thatis, that is, a re-coating of resist is performed and a lithographyprocess is again performed (step 704). When the condition is satisfied,the exposure is continued (step 703).

Moreover, as shown in FIG. 14, both of the dissolved gas concentrationmeter 86 and the particle counter 88 may be connected to the liquiddischarge device 79. In this case, for example, when the both of thecondition in which the concentration of the dissolved gas in thedischarged liquid immersion medium fluid is 0.1 ppm or less and thecondition in which the particle density in the discharged liquidimmersion medium fluid is one piece/ml or less are satisfied, exposureis started or continued, and when any of the conditions is notsatisfied, exposure is cancelled, so that the liquid immersion exposurecan be executed under an appropriate exposure environment.

FIG. 15 is a flowchart showing an example of the liquid immersionexposure method in the just-mentioned case. During the exposure (step901), the dissolved gas concentration and the particle density in thedischarged liquid immersion medium fluid are monitored by the dissolvedgas concentration meter 86 and the particle counter 88 in appropriatetimings or continuously, and it is judged whether or not the conditionsthat the dissolved gas concentration is a predetermined concentration,for example, 0.1 ppm or less, and that the particle density is apredetermined density, for example, one piece/ml or less are satisfied(step 902). When the conditions are not satisfied, the exposure isstopped, and a re-work is carried out, that is, a re-coating of resistis performed and a lithography process is again performed (step 904). Onthe other hand, when the conditions are satisfied, the exposure iscontinued (step 903).

As described above, in accordance with the present embodiment, it ispossible to immediately detect during the exposure the fact that theliquid provided between the lens and the wafer is not clean.Consequently, the liquid immersion exposure processing which may resultin failure finally is rapidly stopped, and the lithography process canbe performed again. As a result, the work efficiency is improved, whichmakes it possible to reduce the cost of manufacturing semiconductordevices to be manufactured.

Sixth Embodiment

FIG. 16 is a view showing a configuration at the time of cleaning of aliquid immersion exposure tool according to a sixth embodiment of thepresent invention. In the configuration of the present embodiment, acleaning device 38 is further provided as compared with theconfiguration of FIG. 10 according to the fifth embodiment of thepresent invention. The cleaning device 38 is connected to the liquidsupply device 76. FIG. 16 shows a situation in which the liquidimmersion exposure tool is operating in a region of the stage 34 wherethere is no semiconductor substrate.

In the present embodiment, portions upper than the head unit are movedafter the exposure to the region of the stage 34 where there is nosubstrate in order to clean the optical lens system 33 and the headunit. Then, a cleaning solution such as ozone water containing cavitiesis supplied into the fence 35 through the liquid supply device 76 fromthe cleaning device 38, so that portions including the optical lenssystem 33 which have been contacted with the liquid immersion mediumfluid are cleaned by the cleaning solution containing cavities.

Thereafter, the cleaning solution remaining in the liquid immersionexposure tool is removed by supplying a rinse solution, for example,water, into the fence 35. However, conventionally, there is no means forconfirming whether or not the cleaning solution has been sufficientlyremoved by the rinse solution. In the present embodiment, aconcentration of ozone or the like included in the rinse solutiondischarged from the fence by the liquid discharge device 79, i.e., therinse solution after being used for rinsing, can be monitored by thedissolved gas concentration meter 86 connected to the liquid dischargedevice 79. Accordingly, it is possible to confirm whether or not thecleaning solution has been sufficiently removed by the rinse solution.When it is confirmed that the cleaning solution has been sufficientlyremoved, liquid immersion exposure is started, and otherwise, therinsing is continued, as it is determined that abnormality has beendetected.

Moreover, even after it is confirmed by the dissolved gas concentrationmeter 86 that the concentration or the like of ozone in the rinsesolution is the predetermined concentration or less, the monitoring maybe continued during the supply of the liquid immersion medium fluid fromthe liquid supply device 76 to determine whether or not the liquidimmersion medium fluid is under an appropriate condition for liquidimmersion exposure. Alternatively, ultrapure water may be used as bothof the rinse solution and the liquid immersion medium fluid. In such acase, ultrapure water is continued to flow, and the dissolved gasconcentration in the discharged water is monitored using the dissolvedgas concentration meter 86. When the dissolved gas concentration is madeto be a predetermined concentration or less, for example, 0.1 ppm orless, the liquid immersion exposure is started. In this manner, liquidimmersion exposure can be executed under an appropriate exposureenvironment after cleaning.

FIG. 17 is a flowchart showing an example of a liquid immersion exposuremethod in the above-mentioned case. After cleaning by a cleaningsolution (step 1101), rinsing is performed with a rinse solution (step1102). While rinsing is being performed, the dissolved gas concentrationin the rinse solution after being used for rinsing is monitored by thedissolved gas concentration meter 86 in appropriate timings orcontinuously, and it is determined whether or not the condition issatisfied in which the dissolved gas concentration is a predeterminedconcentration, for example, 0.1 ppm or less (step 1103). When it isdetermined that the condition is not satisfied, rinsing is continued,and when it is determined that the condition is satisfied, exposure isstarted (step 1104).

In addition, as shown in FIG. 18, a particle counter 88 may be connectedto the liquid discharge device 79, in place of the dissolved gasconcentration meter 86. The particle density of the discharged rinsesolution, i.e., the rinse solution after being used for rinsing ismonitored by the particle counter 88 to determine whether or not theparticle density is a predetermined density, for example, one piece/mlor less. When it is determined that this condition is satisfied, theliquid immersion exposure is started.

FIG. 19 is a flowchart showing an example of a liquid immersion exposuremethod in the just-mentioned case. After cleaning by a cleaning solution(step 1301), rinsing is performed with a rinse solution (step 1302).While rinsing is being performed, the particle density in the dischargedrinse solution, i.e., the rinse solution after being used for rinsing ismonitored by the particle counter 88 in appropriate timings orcontinuously, and it is determined whether or not the condition issatisfied in which the particle density is a predetermined density, forexample, one piece/ml or less (step 1303). When it is determined thatthe condition is not satisfied, the rinsing is continued, and when it isdetermined that the condition is satisfied, exposure is started (step1304).

Further, as shown in FIG. 20, both of the dissolved gas concentrationmeter 86 and the particle counter 88 may be connected to the liquiddischarge device 79. For example, only when the rinse solutiondischarged from the fence 35 by the liquid discharge device 79 satisfiesthe condition in which the dissolved gas concentration is 0.1 ppm orless, and the condition in which the particle density is one piece/ml orless, exposure is started, and exposure is not started when any of theboth conditions is not satisfied, which makes it possible to executeliquid immersion exposure under an appropriate exposure environment.

FIG. 21 is a flowchart showing an example of a liquid immersion exposuremethod in the just-mentioned case. After cleaning by a cleaning solution(step 1501), rinsing is performed with a rinse solution (step 1502).While rinsing is being performed, the dissolved gas concentration in therinse solution after being used for rinsing is monitored by thedissolved gas concentration meter 86 and the particle density in therinse solution after being used for rinsing is monitored by the particlecounter 88 in appropriate timings or continuously. Then, it isdetermined whether or not the conditions that the dissolved gasconcentration is a predetermined concentration, for example, 0.1 ppm orless, and that the particle density is a predetermined density, forexample, one piece/ml or less are satisfied (step 1503). When it isdetermined that the conditions are not satisfied, the rinsing iscontinued, and when it is determined that the conditions are satisfied,exposure is started (step 1504).

Moreover, ozone water is used as a cleaning solution, an ozone gassupply portion 82 and an ozone gas supply device 84 may be provideddirectly beneath portions to be cleaned as shown in FIG. 22.Alternatively, the ozone gas supply portion 82 and the ozone gas supplydevice 84 may be connected to the liquid supply device 76 as shown inFIG. 23. Moreover, a dissolved gas concentration meter 86 and a particlecounter 88 may be provided.

As a consequence, cleaning by ozone water without damaging the lenssurface can be easily attained so as to clean with a ozone concentrationof the ozone water kept constant. At the same time, the ozoneconcentration and particles including ozone bubbles (air bubbles) can bemonitored with the dissolved gas concentration meter 86 and the particlecounter 88. Accordingly, the liquid immersion exposure can be excusedafter confirming that an appropriate exposure environment is establishedafter cleaning.

Further, specifications of the particle density and the dissolved gasconcentration described in the fifth and sixth embodiments varydepending on the liquid immersion exposure conditions to be used (flowrate of liquid, flow method, and the like).

In the above embodiments, examples of the liquid immersion exposure havebeen described. However, the present invention can be applied to liquidimmersion type measuring for measuring a surface of an object.

According to the above-described embodiments, an optical lens system anda liquid immersion medium fluid discharge device or the like configuringthe liquid immersion exposure tool can be cleaned, and the cloudiness ofthe optical lens system can be prevented. In addition, the impuritiesreaching an object surface are reduced, thereby making it possible toprevent contamination on the object surface.

While the above embodiments have described examples of the liquidimmersion exposure tool, the above-described cleaning device is providedat a liquid immersion type microscope for observing a surface of anobject, and a cleaning process may be carried out. Further, theabove-described cleaning device is provided at a liquid immersion typemeasuring instrument for measuring a surface of an object, and acleaning process may be carried out. That is, the above-describedcleaning device is provided at any liquid immersion type equipment, anda cleaning process may be carried out.

In addition, while, in the above embodiments, water has been used as aliquid immersion medium fluid used during liquid immersion, a liquidimmersion medium fluid other than water may be used.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

1. A liquid immersion optical tool comprising: a light source; anoptical lens system; a stage which moves an object base on which anobject is to be placed; a head comprising a liquid immersion mediumfluid supply device and a liquid immersion medium fluid discharge deviceto provide a layer of liquid immersion medium fluid between the opticallens system and the object; a fence which limits a region of the layerof liquid immersion medium fluid; and a cleaning device which cleans aportion having been contacted with the liquid immersion medium fluid bymeans of a cleaning solution.
 2. The liquid immersion optical toolaccording to claim 1, wherein the portion having been contacted with theliquid immersion medium fluid is one or more selected from the groupincluding the optical lens system, the fence, the object base, thestage, the head, the liquid immersion medium fluid supply device, andthe liquid immersion medium fluid discharge device.
 3. The liquidimmersion optical tool according to claim 1, wherein the cleaning devicegenerates cavities in the cleaning solution.
 4. The liquid immersionoptical tool according to claim 3, wherein an average diameter of thecavities is equal to or smaller than 1 μm.
 5. The liquid immersionoptical tool according to claim 1, wherein the cleaning device has anyof a cavitation jet, a venturi tube, a Pitot tube, and a ultrasoundgenerator, and the cavities are generated by any of the cavitation jet,the venturi tube, the Pitot tube, and the ultrasound generator.
 6. Theliquid immersion optical tool according to claim 1, wherein the cleaningdevice is connected to the liquid immersion medium fluid supply device.7. The liquid immersion optical tool according to claim 1, wherein thecleaning device is loaded on the stage.
 8. The liquid immersion opticaltool according to claim 1, wherein the cleaning device is detachable. 9.The liquid immersion optical tool according to claim 1, wherein thecleaning solution is one selected from the group of function watersincluding ozone water, ionized water, carbonated water, and peroxidewater.
 10. The liquid immersion optical tool according to claim 1,wherein the cleaning solution is acid.
 11. The liquid immersion opticaltool according to claim 1, wherein the cleaning solution is water vapor.12. The liquid immersion optical tool according to claim 1, furthercomprising a measuring mechanism which measures intensity of lighttransmitting the optical lens system.
 13. The liquid immersion opticaltool according to claim 12, further comprising: a computing mechanismwhich computes a lowered quantity of light intensity from information onthe light intensity measured by the measuring mechanism; and acalculating mechanism which calculates a period of cleaning by thecleaning device from the computed lowered quantity of light intensity.14. The liquid immersion optical tool according to claim 1, wherein apredetermined pattern is transferred to the object by using the opticallens system.
 15. The liquid immersion optical tool according to claim14, wherein the predetermined pattern is a pattern of a semiconductorelement.
 16. The liquid immersion optical tool according to claim 1,wherein a surface of the object is observed or measured by using theoptical lens.
 17. A cleaning method in the liquid immersion optical toolcomprising a light source; an optical lens system; a stage which movesan object base on which an object is to be placed; a head comprising aliquid immersion medium fluid supply device and a liquid immersionmedium fluid discharge device to provide a layer of liquid immersionmedium fluid between the optical lens system and the object; a fencewhich limits a region of the layer of liquid immersion medium fluid; anda cleaning device which cleans a portion having been contacted with theliquid immersion medium fluid by means of a cleaning solution, whereinthe portion having been contacted with the liquid immersion medium fluidis cleaned for a predetermined time by means of the cleaning device. 18.The cleaning method according to claim 17, wherein a rinse process iscarried out by means of a rinse solution in which no cavities exist,after cleaning by the cleaning solution is carried out for thepredetermined time.
 19. The cleaning method according to claim 18,wherein the rinse solution is water.
 20. A semiconductor devicemanufacturing method in which a semiconductor device is manufactured byusing a liquid immersion exposure tool, the liquid immersion exposuretool comprising: a light source; an optical lens system; a stage whichmoves an object base on which an object is to be placed; a headcomprising a liquid immersion medium fluid supply device and a liquidimmersion medium fluid discharge device to provide a layer of liquidimmersion medium fluid between the optical lens system and the object; afence which limits a region of the layer of liquid immersion mediumfluid; and a cleaning device which cleans a portion having beencontacted with the liquid immersion medium fluid by means of a cleaningsolution.
 21. A liquid immersion optical tool comprising: a lightsource; an optical lens system; a stage which moves an object base onwhich an object is to be placed; a liquid supply device which supplies aliquid immersion medium fluid or a cleaning solution between the opticallens system and the object; a liquid discharge device which dischargesthe liquid immersion medium fluid or the cleaning solution; and an ozonegas supplying device which is connected to the stage or the liquidsupply device and supplies an ozone gas to the cleaning solution.
 22. Aliquid immersion optical tool according to claim 21, further comprisinga measuring device which is connected to the liquid discharge device andmeasures at least one of a dissolved gas concentration and a particledensity of the liquid immersion medium fluid or the cleaning solutiondischarged by the discharge device.
 23. A liquid immersion optical toolaccording to claim 21, wherein the liquid supply device functions togenerate cavities in the cleaning solution.
 24. A liquid immersionoptical tool comprising: a light source; an optical lens system; a stagewhich moves an object base on which an object is to be placed; a liquidsupply device which supplies a liquid immersion medium fluid or acleaning solution between the optical lens system and the object; aliquid discharge device which discharges the liquid immersion mediumfluid or the cleaning solution; and a measuring device which isconnected to the liquid discharge device and measures at least one of adissolved gas concentration and a particle density of the liquidimmersion medium fluid or the cleaning solution discharged by the liquiddischarge device.
 25. A liquid immersion optical tool according to claim24, further comprising an ozone gas supplying device which is connectedto the stage or the liquid supply device and supplies an ozone gas tothe cleaning solution.
 26. A liquid immersion optical tool according toclaim 24, wherein the liquid supply device functions to generatecavities in the cleaning solution.
 27. A cleaning method which cleans anoptical lens system in a liquid immersion optical tool comprising: alight source; the optical lens system; a stage which moves an objectbase on which an object is to be placed; a liquid supply device whichsupplies a liquid immersion medium fluid or a cleaning solution betweenthe optical lens system and the object; a liquid discharge device whichdischarges the liquid immersion medium fluid or the cleaning solution;and an ozone gas supplying device connected to the stage or the liquidsupply device, the method comprising: cleaning the optical lens systemby the cleaning solution in which an ozone gas is dissolved by supplyingthe ozone gas from the ozone gas supplying device to the cleaningsolution.
 28. A cleaning method according to claim 27, furthercomprising generating cavities in the cleaning solution.
 29. A cleaningmethod according to claim 27, further comprising rinsing after thecleaning with a rinse solution, measuring at least one of a dissolvedgas concentration and a particle density of the rinse solution afterbeing used.